Method of manufacturing ultra fine metal powder and ultra fine metal powder manufactured by the same

ABSTRACT

Disclosed are a method of manufacturing ultra fine metal powder used for an electrode for an MLCC and ultra fine metal powder manufactured by the same. The method of manufacturing ultra fine metal powder includes: preparing a master mold in which a pattern is formed; forming a sacrificial layer by applying a polymer material on the pattern; forming a metal layer on the sacrificial layer; and forming individual ultra fine metal powder by removing the sacrificial layer and separating the metal layer from the master mold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No. 10-2010-0103562 filed on Oct. 22, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to ultra fine metal powder and a method of manufacturing the same, and more particularly, to ultra fine metal powder used for an electrode for an MLCC, or the like, and a method of manufacturing the same.

2. Description of the Related Art

As multi-functional electronic products have increased and the propagation of portable electronic devices has increased, components configuring these electronic devices have been miniaturized, while retaining multi-functionality. For example, the development of a small, thin, and large-capacity multilayer ceramic capacitor (MLCC), which is a main component within electronic products, has been actively undertaken.

In order to increase the capacity of a chip product having a predetermined thickness, there is a need to increase the dielectric constant of a dielectric ceramic material or increase the number of electrode layers in the same chip product by thinning dielectric layers and electrode layers in the case of the same material.

To this end, a ceramic green sheet having a thickness of 1 μm or less has recently been developed and a demand for a thin electrode layer has been increased accordingly.

In order to manufacture the thin electrode layer, electrode powder forming the electrode layer needs to be manufactured to have ultra fine powder particles. In the related art, a physical method that mechanically crushes powder particles has mainly used in order to manufacture ultra fine metal powder. However, the physical method has a limitation in the manufacturing of ultra fine metal powder.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method of manufacturing ultra fine metal powder capable of easily manufacturing ultra fine metal powder used for an electrode for an MLCC, or the like and ultra fine metal powder manufactured by the same.

According to an aspect of the present invention, there is provided a method of manufacturing ultra fine metal powder, including: preparing a master mold in which a pattern is formed; forming a sacrificial layer by applying a polymer material to the pattern; forming a metal layer on the sacrificial layer; and forming individual ultra fine metal powder by removing the sacrificial layer and separating the metal layer from the master mold.

The separating may include removing the sacrificial layer by using a solvent dissolving the sacrificial layer.

The separating may include removing the sacrificial layer by applying ultrasonic waves to the sacrificial layer dipped in the solvent.

The polymer material may be ethyl cellulose, polyvinyl butyral (PVB), or polyvinyl alcohol (PVA).

The forming of the sacrificial layer may include: preparing a polymer solution dissolving the polymer material; and applying the polymer solution to the sacrificial layer.

The polymer material may be ethyl cellulose and the polymer solution may have a molecular weight of 40,000 to 200,000.

The polymer material may be polyvinyl butyral (PVB) and the polymer solution may have a molecular weight of 200,000 to 400,000.

The applying of the polymer material may be performed by a spray coating method, a transfer applying method, or a contact applying method.

The forming of the metal layer may be performed by a sputtering method, an electroforming method, a thermal evaporation method, or an e-beam evaporation method.

The sacrificial layer may be formed to have a thickness of 0.1 to 2 μm.

The sacrificial layer may be formed to have a thickness of 1 to 20% with respect to a diameter of the ultra fine metal powder.

The fine metal powder may have a ratio of a width/thickness of 10 to 200 (10:200).

The ultra fine metal powder may be nickel (Ni) powder.

The pattern may be formed to have a lattice shape in which protrusions and grooves are alternately disposed.

The ultra fine metal powder may be manufactured by any one of the above-mentioned methods of manufacturing ultra fine metal powder.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view schematically showing ultra fine metal powder according to an exemplary embodiment of the present invention;

FIG. 2 is a photograph of the ultra fine metal powder according to the exemplary embodiment of the present invention;

FIGS. 3A to 3D are diagrams, each showing a method of manufacturing ultra fine metal powder according to a process sequence according to an exemplary embodiment of the present invention;

FIG. 4A is a photograph showing a plane of a pattern formed in the master mold according to the exemplary embodiment of the present invention;

FIG. 4B is a photograph of a cross section taken along line A-A′ of the master mold shown in FIG. 4A;

FIG. 5 is a photograph of a state in which a sacrificial layer is formed on the pattern of the master mold according to the exemplary embodiment of the present invention; and

FIG. 6 is a flow chart showing the method of manufacturing ultra fine metal powder according to the exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may however be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and dimensions may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like components.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. At this time, it is noted that like reference numerals denote like elements in appreciating the drawings. Moreover, detailed descriptions related to well-known functions or configurations will be ruled out in order not to unnecessarily obscure the subject matter of the present invention. Based on the same reason, it is to be noted that some components shown in the drawings are exaggerated, omitted or schematically illustrated, and the size of each component does not exactly reflect its real size.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view schematically showing ultra fine metal powder according to an exemplary embodiment of the present invention and FIG. 2 is a photograph of the ultra fine metal powder according to the exemplary embodiment of the present invention.

Referring to FIGS. 1 and 2, ultra fine metal powder 32 according to an exemplary embodiment of the present invention is formed to have particles each having a thin flake shape. FIGS. 1 and 2 all show the case in which the ultra fine metal powder 32 is formed to have a rectangular flake shape, but the exemplary embodiment of the present invention is not limited thereto. Therefore, the ultra fine metal powder 32 may be formed in various shapes as necessary, as long as it may be formed to have a flake shape.

In the exemplary embodiment of the present invention, a ratio of width (or diameter)/thickness of the ultra fine metal powder 32 may be 10 to 200.

Further, the ultra fine metal powder 32 according to the exemplary embodiment of the present invention may be nickel (Ni) powder used to manufacture an electrode for a multilayer ceramic capacitor (hereinafter, referred to as MLCC).

As described above, when the ultra fine metal powder 32 is formed to have the flake shape, the size or thickness of the ultra fine metal powder 32 may be formed uniformly and thus, agglomerating the particles of the ultra fine metal powder 32 or forming agglomerates could be solved. This will be described in detail in a method of manufacturing ultra fine metal powder 32 to be described later.

Next, a method of manufacturing ultra fine metal powder according to an exemplary embodiment of the present invention will be described in detail with reference to exemplary embodiments. A configuration of the electrode powder will be more apparent from the following description of the method of manufacturing ultra fine metal powder.

FIGS. 3A to 3D are diagrams, each showing a method of manufacturing ultra fine metal powder according to a process sequence according to an exemplary embodiment of the present invention and FIG. 6 is a flow chart showing the method of manufacturing ultra fine metal powder according to the exemplary embodiment of the present invention.

Referring first to FIG. 3A on the basis of FIG. 6, the method of manufacturing ultra fine metal powder 32 according to the exemplary embodiment of the present invention starts from a step (S10) of preparing a master mold (not shown) in which a pattern 12 is formed.

The master mold according to the exemplary embodiment of the present invention may be formed in a cylindrical drum shape and the pattern 12 maybe formed along the outer peripheral surface thereof.

The exemplary embodiment of the present invention will describe, by way of example, the case in which the pattern 12 is formed on a base film 10 attached to the master mold along the outer peripheral surface of the cylindrical drum shaped master mold. In this case, the base film 10 may be made of polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), or the like, but is not limited thereto.

The method of forming the pattern 12 in the master mold (i.e., base film) may be various. For example, an optical lithography (photolithography) technology using a photosensitive resin based on the shape or dimension of the pattern 12 may be used and a nano imprint lithography (NIL) technology using a ultraviolet curable resin or a thermosetting resin may be used.

In addition, the pattern 12 according to the exemplary embodiment of the present invention may be formed by using a gravure printing technology, a chemical etching method, or the like. In addition, it is possible to form the pattern 12 on the master mold by mechanical direct machining.

FIG. 4A is a photograph showing a plane of a pattern formed in the master mold according to the exemplary embodiment of the present invention and FIG. 4B is a photograph of a cross section taken along line A-A′ of the master mold shown in FIG. 4A. Referring to FIGS. 4A and 4B, the pattern 12 of the master mold according to the exemplary embodiment of the present invention is formed in a lattice shape and are configured such that protrusions and grooves are alternately disposed.

As the pattern 12 is formed as described above, the rectangular ultra fine metal powder 32 may be manufactured by using all of the top surfaces of protrusions and the bottom surfaces of grooves. Further, the master mold according to the exemplary embodiment of the present invention may manufacture the ultra fine metal powder 32 by using the overall area without wasting a space, due to the shape of the pattern 12.

Next, as shown in FIG. 3B, a step (S11) of forming a sacrificial layer 20 on the pattern 12 formed in the master mold is performed.

FIG. 5 is a photograph of a state in which a sacrifice layer is formed on the pattern of the master mold according to the exemplary embodiment of the present invention.

Referring to FIG. 5, the sacrificial layer 20 serves to easily separate the ultra fine metal powder 32 from the master mold while maintaining the shape of the ultra fine metal powder 32, when the ultra fine metal powder 32 is separated from the master mold. To this end, the method of manufacturing ultra fine metal powder according to the exemplary embodiment of the present invention uses the sacrificial layer 20 having a material that is easily dissolved in a specific solvent.

For example, the sacrificial layer 20 according to the exemplary embodiment of the present invention may be made of a polymer material. In addition, the sacrificial layer 20 is made of a material that does not react with the ultra fine metal powder 32.

In more detail, the sacrificial layer 20 according to the exemplary embodiment of the present invention may be made of, for example, ethyl cellulose, among the polymer materials.

The ethyl cellulose has characteristics that are easily decomposed in many solvents such as ethanol, alcohol such as iso propyl alcohol (IPA), or the like, acetone, ketone such as methyl ethyl ketone (MEK), or the like.

In addition, when forming the sacrificial layer 20, a water-soluble resin such as polyvinyl alcohol (PVA), or the like, may be used.

However, the exemplary embodiment of the present invention is not limited thereto, and various polymer materials may be used as long as the materials may be easily decomposed in the solvent and do not react with the ultra fine metal powder 32. For example, polyvinyl butyral (PVB), polystyrene (PS), acrylic resin, or the like, may be used. Alternatively, various kinds of phenol-based resins such as novolac resin may be used.

The sacrificial layer 20 may be formed by applying a solution 50 (hereinafter, a polymer solution) in which polymer materials are dissolved to the pattern 12 of the master mold by using a solvent. In this case, as a solvent material, a material capable of dissolving the polymer materials without deforming the patterns 12 formed on the base film 10 may be used.

In addition, as a method of applying a polymer solution, application methods corresponding to the physical properties of the polymer solution or the shape and characteristics of the patterns 12 may be used. In particular, in order to uniformly form the sacrificial layer 20 on the pattern 12, there is a need to design an appropriate applying process together with selecting the polymer solution.

For example, when the viscosity of the polymer solution is relatively low and the pattern 12 of the master mold is formed to have a fine size, a spray coating method may be used as the application method. In this case, the sacrificial layer 20 may be formed on the pattern 12 with a more uniform thickness by experimentally deriving optimized figures of variables such as the size, pressure, air pressure of a spray nozzle, or the like, as well as the dry characteristics of the polymer solution.

However, the method of applying the polymer solution according to the exemplary embodiment of the present invention is not limited thereto, but various application methods, such as a transfer applying method using a micro gravure process, a contact applying method using a bar-coater, a roller, or the like, may be used.

Meanwhile, the exemplary embodiment of the present invention will describe, by way of example, the case in which Ni powder is manufactured as the ultra fine metal powder 32. In this case, when the size (i.e. diameter) of the Ni powder may be 10 μm or less, the optimal thickness of the sacrificial layer 20 may be 0.1 to 2 μm. When the thickness of the sacrificial layer 20 is calculated by the size of the ultra fine metal powder 32, the thickness of the sacrificial layer 20 may be formed to have a ratio of 1 to 20% with respect to the size (diameter) of the ultra fine metal powder 32.

In addition, the molecular weight of the polymer material used as the sacrificial layer 20 has an effect on the viscosity characteristics of the polymer solution when the polymer solution is manufactured. Therefore, the polymer solution according to the exemplary embodiment of the present invention may have a molecular weight of about 40,000 to 200,000 in the case of ethyl cellulose and may have a molecular weight of about 200,000 to 400,000 in the case of PVB. However, the exemplary embodiment of the present invention is not limited thereto, and the concentration of the polymer solution may be determined at an appropriate level in consideration of the application method or the thickness of the sacrificial layer 20.

Meanwhile, it is important to form the sacrificial layer 20 according to the exemplary embodiment of the present invention on the pattern 12 at an appropriate thickness and the sacrificial layer 20 may be formed to be thicker than thickness of the metal layer 30 formed later. When the sacrificial layer 20 is formed to be too thin (for example, 0.1 μm or less), it is difficult to penetrate a solvent into the sacrificial layer 20 during the separation of the metal layer 30, such that a considerable amount of time and energy may be consumed to separate the metal layer 30. On the other hand, when the sacrificial layer 20 is formed to be too thicker (2 μm or more), the defect in which the shape of the ultra fine metal powder 32 is non-uniformly formed may occur.

Next, as shown in FIG. 3C, a step (S12) of forming the metal layer 30 on the sacrificial layer 20 is performed.

As described above, the exemplary embodiment of the present invention will describe, by way of example, the case in which Ni powder is manufactured as the ultra fine metal powder 32. Accordingly, a nickel (Ni) layer is formed on the sacrificial layer 20 as the metal layer 30.

The metal layer 30 may be manufactured by various evaporation methods. For example, an electroforming process may be used. Describing this in more detail, in the step (S12) of forming the metal layer 30 according to the exemplary embodiment of the present invention, a thin metal seed layer may be formed on the sacrificial layer 20 by the sputtering method, or the like, and then, the electroforming process may be performed on the metal seed layer to form the metal layer 30 having a desired thickness.

The electroforming process is mainly used in the case in which the thickness of the finally formed metal layer 30 is several tens of μm or more. Therefore, the electroforming process may be used to form a metal flake having a size thicker than that of the ultra fine metal powder 32 or a plating layer.

On the other hand, when forming the metal layer 30 having a thin thickness of several tens of nm to several μm like the ultra fine metal powder 32, physical evaporation methods such as thermal evaporation, e-beam evaporation, sputtering, or the like, maybe used. The metal layer 30 according to the exemplary embodiment of the present invention may be formed to have a thickness of 10 nm to 100 nm by the evaporation methods. However, the present invention is not limited thereto.

Next, as shown in FIG. 3D, a step (S13) of separating the metal layer 30 from the master mold is performed.

The metal layer 30 according to the exemplary embodiment of the present invention is separated from the master mold by removing the sacrificial layer 20 interposed between the master mold and the metal layer 30.

To this end, the method of manufacturing ultra fine metal powder 32 according to the exemplary embodiment of the present invention removes the sacrificial layer 20 by dipping the master molder (hereinafter, referred to as a metal structure), in which the sacrificial layer 20 and the metal layer 30 are stacked, in a specific solvent 50 (hereinafter, referred to as a polymer decomposition solvent) easily dissolving the sacrificial layer 20.

For example, when the ethyl cellulose is used as a polymer material, the ethyl cellulose represents the excellent solubility in ethanol, toluene, or a mixing solvent thereof. Therefore, when the metal structure is dipped in the polymer decomposition solvent 50, the sacrificial layer 20 made of the ethyl cellulose is easily dissolved by the polymer decomposition solvent 50, such that the metal layer 30 is separated from the metal structure and is made of the individual ultra fine metal powder 32 as shown in FIG. 1.

In this case, the method of forming ultra fine metal powder according to the exemplary embodiment of the present invention may use ultrasonic waves in order to smoothly separate the metal layer 30. That is, the dissolution of the sacrificial layer 20 may be accelerated by applying ultrasonic waves to the metal structure dipped in the polymer decomposition solvent 50 in which the sacrificial layer 20 is dissolved.

The ultrasonic treatment may be unnecessary according to the shape or size of the pattern 12, but the polymer decomposition solvent 50 may be more easily penetrated into the sacrificial layer 20 when using the ultrasonic waves, such that the dissolution rate of the sacrificial layer 20 is faster. Therefore, the process of separating the metal layer is performed within a relatively short time.

The ultrasonic waves may be applied by a separately provided ultrasonic vibrator (not shown). However, various devices may be used, as long as the device may apply the ultrasonic waves to a container in which the polymer decomposition solvent 50 and the metal structure are dipped.

In addition, in order to easily extract the ultra fine metal powder 32 separated from the metal structure, it is possible to additionally use a magnet.

The ultra fine metal powder 32 according to the exemplary embodiment of the present invention manufactured by the above-mentioned methods may be variously used.

For example, a conductive paste may be manufactured by mixing the ultra fine metal powder 32 according to the exemplary embodiment of the present invention, with a resin binder, and an organic solvent. In this case, an alkyd resin, the ethyl cellulose, or the like, all of which are organic compounds easily removed during the firing process may be used as the resin binder, and terpineol, butyl carbitol acetate, kerosene, or the like, all of which are organic compounds easily volatilized by the drying process after appropriately imparting viscosity to the paste and being applied to the green sheet, may be used as the organic solvent.

The conductive paste according to the exemplary embodiment of the present invention manufactured as described above may be used to form the electrode (for example, nickel (Ni) electrode) when manufacturing the electronic devices (for example, MLCC).

As described above, the ultra fine metal powder according to the exemplary embodiment of the present invention may be the nickel (Ni) electrode powder for the MLCC and formed to have a flat flake shape having an uniform size. As a result, when the conductive paste or the electromagnetic wave shielding material is manufactured by using the ultra fine metal powder according to the exemplary embodiment of the present invention, since the ultra fine metal powder have an uniform size, the electrode layer having very high packing density and electrode connectivity could be formed before and after the heat treatment process such as the firing process, or the like. Accordingly, according to the exemplary embodiment of the present invention, the defect of the degradation in electrode connectivity due to the high-temperature contraction may be minimized while allowing the electrode for the MLCC to be formed thinner.

Further, according to the method of manufacturing ultra fine metal powder according to the exemplary embodiment of the present invention, the ultra fine metal powder is manufactured by using a pattern, such that the shape of the ultra fine metal powder could be freely controlled, thereby easily manufacturing the ultra fine metal powder having a specific shape.

In addition, according to the exemplary embodiment of the present invention, even though the ultra fine metal powder having a very thin thickness is manufactured, the ultra fine metal powder could be easily separated from the master mold by the sacrificial layer. As a result, according to the exemplary embodiment of the present invention, the ultra fine metal powder could be easily separated without damaging the pattern of the master mold or the ultra fine metal powder.

On the other hand, in the related art, powder particles having shapes other than a spherical shape may be obtained by using only the mechanical machining method, such that the shapes or sizes of the powder particles are non-uniform and it is difficult to control the thicknesses of the powder particles. This leads to agglutination of the powder or formation of agglomerates.

However, the method of manufacturing ultra fine metal powder according to the exemplary embodiment can manufacture the powder particles having an uniform size and shape and extract the powder individually dispersed from the solvent, such that it can minimize the above-mentioned defects.

Meanwhile, the method of manufacturing ultra fine metal powder and the ultra fine metal powder manufactured by the same according to the exemplary embodiment of the present invention described above are not limited to the above-mentioned method and therefore, various applications can be made. For example, the above-mentioned exemplary embodiments of the present invention described, by way of example, the case in which the pattern is formed in a lattice shape, but the exemplary embodiment of the present invention is not limited thereto. As a result, the pattern may be formed in various shapes such as a circular shape, a triangular shape, a rectangular parallelepiped shape, or the like, as necessary, thereby manufacturing corresponding ultra fine metal powder.

Further, the above-mentioned exemplary embodiment described, by way of example, the case in which the electrode powder is manufactured, but the exemplary embodiment of the present invention is not limited thereto. As a result, the exemplary embodiment of the present invention may be easily applied to all the cases in which the metal is manufactured to have a flake shape.

While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims. 

1. A method of manufacturing ultra fine metal powder, comprising: preparing a master mold in which a pattern is formed; forming a sacrificial layer by applying a polymer material to the pattern; forming a metal layer on the sacrificial layer; and forming individual ultra fine metal powder by removing the sacrificial layer and separating the metal layer from the master mold.
 2. The method of claim 1, wherein the separating includes removing the sacrificial layer by using a solvent dissolving the sacrificial layer.
 3. The method of claim 2, wherein the separating includes removing the sacrificial layer by applying ultrasonic waves to the sacrificial layer dipped in the solvent.
 4. The method of claim 1, wherein the polymer material is ethyl cellulose, polyvinyl butyral (PVB), or polyvinyl alcohol (PVA).
 5. The method of claim 1, wherein the forming of the sacrificial layer includes: preparing a polymer solution dissolving the polymer material; and applying the polymer solution to the sacrificial layer.
 6. The method of claim 5, wherein the polymer material is ethyl cellulose and the polymer solution has a molecular weight of 40,000 to 200,000.
 7. The method of claim 5, wherein the polymer material is polyvinyl butyral (PVB) and the polymer solution has a molecular weight 20,000 to 40,000.
 8. The method of claim 5, wherein the applying of the polymer material is performed by a spray coating method, a transfer applying method, or a contact applying method.
 9. The method of claim 1, wherein the forming of the metal layer is performed by a sputtering method, an electroforming method, a thermal evaporation method, or an e-beam evaporation method.
 10. The method of claim 1, wherein the sacrificial layer is formed to have a thickness of 0.1 to 2 μm.
 11. The method of claim 1, wherein the sacrificial layer is formed to have a thickness of 1 to 20% with respect to a diameter of the ultra fine metal powder.
 12. The method of claim 1, wherein the fine metal powder has a ratio of a width/thickness of 10 to 200 (10:200).
 13. The method of claim 1, wherein the ultra fine metal powder is nickel (Ni) powder.
 14. The method of claim 1, wherein the pattern is formed to have a lattice shape in which protrusions and grooves are alternately disposed.
 15. An ultra fine metal powder manufactured by the method of manufacturing ultra fine metal powder claimed in claim
 1. 